CCI-779 is a rapamycin analog cell cycle inhibitor currently in clinical development for cancer treatment. CCI-779 inhibits the mammalian target of rapamycin (mTOR) kinase which is a downstream mediator in the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway resulting in cell cycle arrest and induction of apoptosis. Previous data from our group suggest that CCI-779 is particularly effective in inhibiting the growth of cancer cells with hyperactivation in the PI3K/Akt signaling pathway as a result of deletions of the PTEN tumor suppressor gene. In addition, we have developed and optimized analytical methods to measure Akt activation in tumor tissues as well as the biological effects of CCI-779 in clinical specimens. Our long term goal is to optimally develop CCI-779 for the treatment of patients with cancer utilizing rationally-derived biological concepts. The objective of this research proposal is to determine the relationship between Akt hvperactivation in tumor tissues and the biological effects of CCI-779 on its target pathway with indices of outcome. The central hypothesis of the proposed research is that the therapeutic role of CCI-779 will be maximal in patients with Akt hyperactivated tumors in whom treatment with the agent inhibits mTOR signaling. We have elected to test this hypothesis in patients with recurrent glioblastoma multiforme due to the high frequency of PTEN mutations (30-40 percent) that result in Akt hyperactivation in this disease. In Specific Aim # 1, we will determine the relationship between Akt hyperactivation and outcome of patients with recurrent malignant glioblastoma who are treated with CCI-779. In Specific Aim # 2, we will relate the biological effects of CCI-779 on mTOR signaling in clinical specimens obtained from patients treated with the agent with parameters of outcome. Patients with recurrent malignant glioblastoma multiforme will be treated with CCI-779 under a National Cancer Institute (NCI) sponsored phase II study. Akt activation will be determined in tumor tissues using immunohistochemical methods previously developed by our group. The biological effects of CCI-779 will be measured in peripheral blood mononuclear cells (PBMC) using a kinase assay. The quantitative results of the biological tests will be related to indices of patient's outcome using uni and multivariate statistical methods. This proposal is innovative because it incorporates measurement of biological functions related to the molecular target of this novel agent to optimize its clinical development. The principal significance of these studies will be to provide hypothesis-generating data with regards to tailoring treatment with CCI-779 to patients most likely to benefit by this novel agent based on both molecular and pharmacodynamic factors.